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Unexpected behaviour of UART in K22 when baud rate is changed

Question asked by Vaibhavi P on Jan 10, 2020
Latest reply on Feb 12, 2020 by Gaurav More



I am using custom board with MK22FX512AVLQ12. I am using UART of the controller with baud rate set as 19200 and Parity Even. I am using an external application to send and receive data from UART. The parity is set to Even at the external aplication side.


I am performing the following sequence of operation:

1. Send data frame at 19200 : Uart replies correctly as expected

2. In the external application, Change the baud rate to some other value (e.g. 57600) and send data to UART : UART       sends no reponse (as expected)

3. In the external application, Change the baud rate to 19200 (corret baud rate) again, and send data to UART : UART       sends no reponse, which is not expected since the baud rates are matched now.

4. Now if I restart the controller through software and then send the data at 19200: the UART sends the resopnse as       expected.


I have same obervation on FRDM K22 Evaluation board.


I am unable to understand the reason behind such behaviour. Please help in understanding the reason behind this.

Also please suggest a way by which software restart would not be reqiured in above operations.


Thanks and Regards,